In the manufacture of microelectronic devices, such as processors, controllers, and memory, the desired structures are formed on a wafer. Individual dies are cut from the wafer and then sealed into a package. The package has an array of pins, pads, or lands that make contact with the rest of the device, typically through a printed circuit board to allow the die to be operated while within the package. After packaging, each package is tested to ensure that it has been manufactured correctly and operates as intended.
To perform the tests, the packages may have lands, pads, or balls specifically designed into the package for test purposes. There is also an array of contacts that are used for normal operations. These are often, but not always, in the form of solder balls. Spring loaded pins or probes are applied to the lands or balls and signals are sent or received through the pins to test the die.
The test probes are in the form of spring and sleeve connectors in which one or both ends of the probe are spring-loaded to apply pressure against the electrical contacts of the package. One common type of spring loaded probe is referred to as a pogo pin. The test probes are mounted to a circuit board or attached to a substrate in a socket that holds each cylinder in the proper position with respect to each other probe so that when the package is pressed against the socket, each probe will contact its respective ball or pad. The probes are spring loaded and have a shaped tip so that when the probes are pressed against the package the pressure will stress and break through any oxide that has formed on the surface of the solder or other material of the electrical contact to ensure a good electrical connection.
The tip of each spring and sleeve connector wears with each new contact and may also collect contaminants from the package connection. As a result, each test probe has a limited number of contacts and therefore a limited number of package tests that it can perform. After which the test probe is replaced. With thousands of test probes in each socket, test probe replacement is a factor in the cost of die manufacturing.